LANZHOU - An overloaded bus overturned Sunday on a highway in Gansu province, leaving four dead and eight others seriously injured, local authorities announced Monday.

The accident occurred around 8 pm Sunday on a highway in Yongjing county when the bus was traveling from the county's Liujiaxia township to the nearby Yan'guoxia township, the Gansu Provincial Work Safety Bureau said in a statement.

The 19-seat bus was carrying 34 people when it rolled, according to the statement.

The four deceased all died in hospital.

An initial investigation has found that the vehicle was not licensed for public transport.

Local authorities are further investigating the accident.